In electric power plants such as nuclear power plants and thermal power plants, petroleum refining, petrochemical plants, and liquefied natural gas (LNG) plants, electricity is generated or power sources of compressors are used by supplying steam generated in plant processes to steam turbines and rotatably driving generators, compressors, and the like coupled to rotors of steam turbines. Turbine trips in which rotation of such steam turbines is quickly stopped are performed on the steam turbines and thus machines are protected in an emergency in which it is difficult to safely operate rotating bodies and plant machines. Turbine trips are performed by closing main steam stop valves provided in supply passages used to supply steam to steam turbines and by cutting off the supply of steam to the steam turbines.
An emergency shutoff device configured to perform such a turbine trip is disclosed, for example, as a turbine emergency device in Patent Document 1. The turbine emergency device disclosed in Patent Document 1 has a plurality of electromagnetic valves and a plurality of master trip valves, which configured to control the supply of control oil to a steam stop valve serving as a main steam stop valve. In such a turbine emergency device, a spool is formed such that a closing port and an oil pressure supply port which are not used during a normal operation communicate with each other at all times in a spool valve constituting a master trip valve.